Add notice that chapter names are for future DVD menu support

Added italic note "(For future DVD menus)" below chapter title entry
fields to inform users that:
- Chapter markers work and allow navigation between scenes
- Chapter names are saved but not displayed in basic DVDs
- Names will be used when DVD menu system is implemented

This prevents users from wasting time entering custom chapter names
expecting them to appear in DVD players, while preserving the data
for future menu implementation.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

author_module.go

@@ -321,8 +321,12 @@ func buildVideoClipsTab(state *appState) fyne.CanvasObject {
 
 	listArea := container.NewMax(dropTarget, emptyOverlay)
 
+	// Note about chapter names
+	chapterNote := widget.NewLabel("Chapter names are saved for future DVD menu support")
+	chapterNote.TextStyle = fyne.TextStyle{Italic: true}
+
 	controls := container.NewBorder(
-		widget.NewLabel("Videos:"),
+		container.NewVBox(widget.NewLabel("Videos:"), chapterNote),
 		container.NewVBox(chapterToggle, container.NewHBox(addBtn, clearBtn, addQueueBtn, compileBtn)),
 		nil,
 		nil,